1. Field of the Invention
This invention relates to gas pressure increasing systems including a freezing apparatus, a refrigerating apparatus and an air conditioning system using a scroll compressor as a compressor means and an apparatus in which air or other gas is compressed by a scroll compressor to increase its pressure.
2. Description of the Prior Art
A scroll compressor has been used as a compressor means of a gas pressure increasing system including a compressor means, a condenser, an expanding or pressure reducing means and an evaporator or a gas pressure increasing system including a compressor means and a gas cooler.
A scroll comressor comprises an orbiting scroll member and a fixed scroll member, the orbiting scroll member including an end plate and a wrap formed primarily in an involute curve and attached to one surface of the end plate in an upstanding position and the fixed scroll member including an end plate, a wrap formed primarily in an involute curve and attached to one surface of the end plate in an upstanding position, a suction port and an exhaust port. The orbiting scroll member and fixed scroll member are arranged in juxtaposed relation with the wraps thereof being fitted closely together, and the orbiting scroll member is moved in orbiting motion by a drive shaft from a motor while the rotation of the orbiting scroll member on its own axis is inhibited by an Oldham's ring interposed between the orbiting and fixed scroll members or between the orbiting scroll member and a housing. The orbiting movement of the orbiting scroll member reduces sealed spaces defined between the two scroll members and compresses a gas therein to increase its pressure.
A scroll compressor, an expanding machine and a pump having the aforesaid construction are disclosed in U.S. Patent No. 3,884,599.
In a scroll compressor, and expanding machine and a pump (hereinafter generally referred to as scroll fluid apparatus), the pressure of a gas in the sealed spaces defined between the orbiting scroll member and fixed scroll member becomes high as portions of the wraps of the two scroll members in contact with each other approach the center of each wrap. This increase in pressure occurs periodically during the orbiting movement of the orbiting scroll member, so that a force urging the two scroll member away from each other is produced between them. In the event the two scroll members being separated from each other by such force, gaps will be produced between the tops of the wraps and the two end plates, and an axial seal will not be provided satisfactorily. The result of this is that a leakage of gas through the gaps will increase and the efficiency of the scroll fluid apparatus will be reduced.
In order to provide a satisfactory axial seal, U.S. Patent No. 2,841,089 proposes to use compression springs mounted between a surface of the orbiting scroll member which is opposite to the surface provided with a wrap and a housing to urge the orbiting scroll member to move toward the fixed scroll member. In U.S. Patent No. 3,600,114, an exhaust gas from an exhaust gas line of the scroll compressor is introduced into a space formed on a surface of the orbiting scroll member which is opposite to the surface provided with a wrap so as to bring the pressure of the exhaust gas of the compressor itself to bear upon the orbiting scroll member. U.S. Patent No. 3,884,599 provides means for applying the pressure of an exhaust gas of the scroll compressor itself and the pressure of a spring to the orbiting scroll member.
Some disadvantages are associated with the aforementioned proposals of the prior art made for the purpose of providing a satisfactory axial seal to the orbiting scroll member of a scroll compressor. When the pressure of springs is utilized, springs should be mounted between a movable part (orbiting scroll member) and a stationary part (housing), resulting in an increase in the area of the sliding portion and an attendant frictional loss. Also, since the force imparted by springs is substantially constant, a large imbalance would occur between the force urging the two scroll members away from each other and the force imparted by the springs when the pressure of a gas in the sealed spaces is low, such as the time of starting. Owing to such imbalance, the frictional dragging of the orbiting scroll member on the fixed scroll member would be great and consequently the starting torque would become very high.
The use of the pressure of an exhaust gas from an exhaust gas line of the scroll compressor itself would have the disadvantage that if the pressure of the exhaust gas is applied directly or indirectly to the surface of the orbiting scroll member which is opposite to the surface provided with a wrap, an axial force far greater than a force necessary for providing an axial seal (which is slightly greater than a force urging the two scroll members away from each other) would be produced, thereby increasing a frictional loss between the two scroll members. This would necessitate the provision of means for limiting the pressure receiving area to a low level which would in turn render the construction of the scroll compressor complex.
In each of the prior art referred to hereinabove, means for producing a force necessary for providing an axial seal are described by referring to various embodiments as examples. However, there is not expressly mentioned therein a means of removing heat which would be produced by compression and friction as well as the heat produced by an electric motor.